It's pretty simple. What I do is plop 'em in warm water (or even lukewarm. NOT hot, because then you can get explodo-rats) for as long as it takes to soften up completely. And serve!! If you want, you can dry them off, but it's not necessary. I just like to.
If you have a picky eater, in addition you can try sticking the (thawed) feeder directly below a heat lamp for 2-5 minutes to give it the illusion of normal body temperature.